Doc modding Marantz imperial 7

[karatestu]

I have now babbled on for 150 pages of waffle.

Painting plastic - as well as plasti dip primer and top coat I am going to try etch primer or pva before priming. The advantage of using acrylic would have been no finishing required but hey you can't have it all ways.

[CycleCoach]

Are you going to build first to check they work, or paint and then assemble?
Seriously loving your "outside the box" thinking.

[CycleCoach]

Are you going to build first to check they work, or paint and then assemble?
Seriously loving your "outside the box" thinking.

Build to check it all works first then finish. I am testing the finishing process on a ball which I won't be using as I cut holes big enough for the face plate. The bad thing about painting them last is that if they work as intended then I will be too glued to listening to them that I won't want to take them to pieces

"outside the box" - ha ha. I know the tweeter spheres work because i have one assembled with gaffa tape at the moment. The mid bass sphere is where I am still in the dark. Smooth spheres have the most effect with high frequencies. To get an effect lower down the spheres have to get bigger. In the case of doing this with a doped mid bass which is still producing useful output up to 10kHz then it is very much worth doing I think. If it was a woofer crossed over to a mid at say 200Hz then it would not have an effect apart from the sound waves coming from the mid and tweeter.

Anyway, I think it would look daft having a tweeter and a mid in their own sphere(s) and then sitting it on top of a cube woofer enclosure.

Thanks for spurring me on

[Geoff.R.G]

Are you going to build first to check they work, or paint and then assemble?
Seriously loving your "outside the box" thinking.

Build to check it all works first then finish. I am testing the finishing process on a ball which I won't be using as I cut holes big enough for the face plate. The bad thing about painting them last is that if they work as intended then I will be too glued to listening to them that I won't want to take them to pieces

"outside the box" - ha ha. I know the tweeter spheres work because i have one assembled with gaffa tape at the moment. The mid bass sphere is where I am still in the dark. Smooth spheres have the most effect with high frequencies. To get an effect lower down the spheres have to get bigger. In the case of doing this with a doped mid bass which is still producing useful output up to 10kHz then it is very much worth doing I think. If it was a woofer crossed over to a mid at say 200Hz then it would not have an effect apart from the sound waves coming from the mid and tweeter.

Anyway, I think it would look daft having a tweeter and a mid in their own sphere(s) and then sitting it on top of a cube woofer enclosure.

Thanks for spurring me on

Theory says that low frequencies don't contribute to imaging so you could just have a woofer out of sight and keep the mid and tweeter in their own spheres without any need to sit on a, square, bass bin.

[karatestu]

Theory says that low frequencies don't contribute to imaging so you could just have a woofer out of sight and keep the mid and tweeter in their own spheres without any need to sit on a, square, bass bin.

Of course Geoff. But I am Like the Doc when I think all drivers should be as close to each other as possible and time aligned. Because of that, if I were to be making a three way like then I would probably put them on top of each other and all in spheres. Just me.

Good point about low frequencies not contributing to imaging. Apparently the frequency where we start to be able to localise the source of a sound is about 80 -100Hz. Surely it would have to be a sub woofer if it was going to be away from the main speakers ?

Isn't most bass content that we hear below a certain frequency in mono ?

[karatestu]

Done a bit of work on the tweeter pod today. One tweeter fitted in with no face plate and the terminal tab removed. Tinsel wires are yet to be extended and routed to the back of the driver



Not quite lined up properly yet but you get the picture





This is turning into one of the biggest ball aches ever and I have eight to do I am seriously considering putting some face plates on but not the originals. I have some 0.5mm copper sheet that might look good when polished up and lacquered. The original face plates are 2.5mm so that would be a lot thinner. The voice coil needs to be not able to move and the little screws that hold it on are now too long and the head sticks up. I will need to countersink the plastic front and reduce the length of the screws if I carry on with the no face plate idea.

If do put a copper face plate on I will stick to the 68mm diameter that I have now so will have to remove all the wire terminal tabs but i can live with that.

[karatestu]

I might have to flame treat this plastic to get better adhesion. Time to get the propane torch out. You need to apply the paint or glue within 30 min of flame treating. It involves passing the outer edge of a flame very quickly over the plastic surface.

I think etching primer is going to ge useless on this plastic. At the moment it is coming off really easy. The plasti dip primer on the other hand seems to be working really well.

[karatestu]

A link to spherical speakers that I had not seen before. Interesting stuff, especially the bit about the so called strong "standing wave" at one frequency due to having one internal dimension where the author found there was not a problem. All very encouraging

http://www.speakerdesignworks.co ... ns.html

[karatestu]

This paragraph does chime with me with what I have experienced so far. Spaciousness, lovely spaciousness which is so smooth and inviting. I think it suits the pseudo omni directional nature of my speakers and enhances it. I like Spaciousness, it's so inviting and draws you in like nothing I have had at home. It's almost like you can walk in to the room full of musicians.

"Other than the baffle step, the normal baffle
edge diffraction effects are ameliorated, as the
wave front appears to follow the curve of the
sphere. Just exactly how the wave front
propagates around the sphere may be open
for debate, but I can say that from my empirical
observations and measurements indicate it
provides a smoother off-axis response. The
resultant in room sound is quite spacious,
similar to, but not as manifest as a dipole. The
imaging and power response also hold up
nicely off axis."

[Geoff.R.G]

A link to spherical speakers that I had not seen before. Interesting stuff, especially the bit about the so called strong "standing wave" at one frequency due to having one internal dimension where the author found there was not a problem. All very encouraging

http://www.speakerdesignworks.co ... ns.html

What is it with Hi-Fi and standing waves?